Use of in vivo Whole-Body Autoradiography to Identify the Distribution of Epidermal Growth Factor Binding Sites under Normal Conditions in the Mouse Digestive System.

Abstract

The distribution of epidermal growth factor (EGF) binding sites in the mouse digestive system was investigated by in vivo whole-body autoradiography. Male mice were injected intravenously with 125I-EGF in both the absence and the presence of excess unlabeled EGF. The animals were perfused and subjected to autoradiographic procedures 3, 5, 15, and 30min after injection. Our study provides the first quantitative data on the binding levels of digestive system tissues under in vivo conditions with intact experimental mice.Specific EGF binding was observed in the liver, pancreas, stomach, and intestinal mucosae at 3, 5, and 15min post-injection, but at 30 minutes the bindings were not lowered by the presence of excess unlabeled EGF. Very high specific EGF binding was noted in the liver, where distribution of the binding sites was heterogeneous, and the density of the binding was higher around the branches of the portal vein than around the central vein. In the stomach, relatively high specific binding was seen in the glandular part, but the non-glandular portion showed no significant binding. There was low specific binding in the pancreas and distribution of that binding was homogeneous according to macroscopic observation. Low specific binding was observed in the intestinal tract from duodenum to rectum, and level of the binding was quite similar throughout the tract. The esophagus evinced no substantial EGF binding. Submandibular and sublingual glands showed relatively high radioactivity during the experimental period, but most of it was nonspecific in nature.